Administration of radiolabelled antibodies is a relatively new treatment modality for certain forms of cancer. Much of this field is developmental in nature. In particular, the dosimetry of tumor masses and adjacent body structures and tissues is still a complex set of problems. The Radiation Physics and Computer Automation Section is attempting a novel approach employing computer aided convolution of CT density distributions into scout film images, and "loaded" with radioactivity, into simulated gamma camera images. By means of iterative procedures, starting from images of known activity distributions, it hoped to gain insight in the quantitative distribution of radioactivity on the basis of intrinsically low resolution gamma camera images of real patient MAb distributions.